a.underline {
  text-decoration: none;
  background-image: linear-gradient(transparent, transparent 6px, #34495e 6px, #34495e);
  background-position: bottom;
  background-size: 100% 6px;
  background-repeat: repeat-x;
}

a.underline:hover {
  background-image: linear-gradient(transparent, transparent 4px, #1d1d1d 4px, #1d1d1dff);
}
